Re: [PATCH 3/7] xfs: fix a bug in the online fsck directory leaf1 bestcount check

Dave Chinner
2021-12-16T22:04:12Z

On Wed, Dec 15, 2021 at 05:09:32PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> When xfs_scrub encounters a directory with a leaf1 block, it tries to
> validate that the leaf1 block's bestcount (aka the best free count of
> each directory data block) is the correct size. Previously, this author
> believed that comparing bestcount to the directory isize (since
> directory data blocks are under isize, and leaf/bestfree blocks are
> above it) was sufficient.
>
> Unfortunately during testing of online repair, it was discovered that it
> is possible to create a directory with a hole between the last directory
> block and isize. The directory code seems to handle this situation just
> fine and xfs_repair doesn't complain, which effectively makes this quirk
> part of the disk format.
>
> Fix the check to work properly.
>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>

With the "we're not sure how this happens" discussion out of the
way, the change to handle the empty space between the last block and
isize looks fine.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
--
Dave Chinner
david@fromorbit.com